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/* Machine-dependent pthreads configuration and inline functions.
i386 version.
Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Richard Henderson <rth@tamu.edu>.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <http://www.gnu.org/licenses/>. */
#ifndef _PT_MACHINE_H
#define _PT_MACHINE_H 1
#include <features.h>
#ifndef __ASSEMBLER__
#ifndef PT_EI
# define PT_EI __extern_always_inline __attribute__((visibility("hidden")))
#endif
extern long int testandset (int *spinlock);
extern int __compare_and_swap (long int *p, long int oldval, long int newval);
/* Get some notion of the current stack. Need not be exactly the top
of the stack, just something somewhere in the current frame. */
#define CURRENT_STACK_FRAME __builtin_frame_address (0)
/* See if we can optimize for newer cpus... */
#if defined __GNUC__ && __GNUC__ >= 2 && \
(defined __i486__ || defined __pentium__ || defined __pentiumpro__ || defined __pentium4__ || \
defined __athlon__ || defined __k8__)
/* Spinlock implementation; required. */
PT_EI long int
testandset (int *spinlock)
{
long int ret;
__asm__ __volatile__ (
"xchgl %0, %1"
: "=r" (ret), "=m" (*spinlock)
: "0" (1), "m" (*spinlock)
: "memory");
return ret;
}
/* Compare-and-swap for semaphores. It's always available on i686. */
#define HAS_COMPARE_AND_SWAP
PT_EI int
__compare_and_swap (long int *p, long int oldval, long int newval)
{
char ret;
long int readval;
__asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
: "=q" (ret), "=m" (*p), "=a" (readval)
: "r" (newval), "m" (*p), "a" (oldval)
: "memory");
return ret;
}
#if defined(__ASSUME_LDT_WORKS) && __ASSUME_LDT_WORKS > 0
#include "useldt.h"
#endif
/* The P4 and above really want some help to prevent overheating. */
#define BUSY_WAIT_NOP __asm__ ("rep; nop")
#else /* Generic i386 implementation */
extern int compare_and_swap_is_available (void);
/* Spinlock implementation; required. */
PT_EI long int
testandset (int *spinlock)
{
long int ret;
__asm__ __volatile__(
"xchgl %0, %1"
: "=r"(ret), "=m"(*spinlock)
: "0"(1), "m"(*spinlock)
: "memory");
return ret;
}
/* Compare-and-swap for semaphores.
Available on the 486 and above, but not on the 386.
We test dynamically whether it's available or not. */
#define HAS_COMPARE_AND_SWAP
#define TEST_FOR_COMPARE_AND_SWAP
PT_EI int
__compare_and_swap (long int *p, long int oldval, long int newval)
{
char ret;
long int readval;
__asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
: "=q" (ret), "=m" (*p), "=a" (readval)
: "r" (newval), "m" (*p), "a" (oldval)
: "memory");
return ret;
}
PT_EI int
compare_and_swap_is_available (void)
{
int changed;
int oldflags;
/* get EFLAGS */
__asm__ __volatile__ ("pushfl; popl %0" : "=r" (oldflags) : );
/* Flip AC bit in EFLAGS. */
__asm__ __volatile__ ("pushl %0; popfl" : : "r" (oldflags ^ 0x40000) : "cc");
/* reread EFLAGS */
__asm__ __volatile__ ("pushfl; popl %0" : "=r" (changed) : );
/* See if bit changed. */
changed = (changed ^ oldflags) & 0x40000;
/* Restore EFLAGS. */
__asm__ __volatile__ ("pushl %0; popfl" : : "r" (oldflags) : "cc");
/* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
Otherwise, it's a 486 or above and it has cmpxchg. */
return changed != 0;
}
#endif /* Generic i386 implementation */
#endif /* __ASSEMBLER__ */
#endif /* pt-machine.h */
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